Tag Archives: Carbon dioxide

Does it matter if I eat acid-forming foods? Not when you look at the research.

There is a widespread idea among health-seeking eaters that one ought to avoid meat, dairy and other “acid-forming foods” in favor of vegetables. The theory is that your body needs alkalizing foods or acid blood will leach minerals from your bones . Generally the effect is to get people to eat more vegetables, but after reading about this for 20 years I have to say that the evidence for the theory itself isn’t compelling.

First, what is an acid-forming food?  Lemon juice is acid but it stimulates the release of magnesium which alkalizes.  Vinegar (another acid) gets classified both ways, but it does function similarly to lemon juice.  The makers of alkaline water like Kangen believe that alkaline water makes the body alkaline.  Generally meat, dairy, sugars and some fruits are shown on the “acidifying” side while vegetables, good oils and most fruits (except blackberries) are shown as “alkalizing”.  Some of the foods on lists are backed by research from the 50s and 60s, while others are conjecture.  The problem is that the body has complicated feedback systems, food is eaten in groups and at different times of the day and constitutions differ.

A healthy stomach secretes gastric acid at a  pH of 1.5  to digest food, including meat, and that extreme acidity triggers the esophageal sphincter to shut.  The acid kills disease-bearing organisms and opens the sphincter at the bottom of the stomach to let the food get treated by bile, probiotic organisms and the intestines.  If you have reflux, you generally have too little acid, so the esophageal sphincter doesn’t close and the lesser acid bubbles up where it can cause harm. (Starting the meal with bitters can help your liver and stomach produce sufficient acid, but you may need to take betaine hydrochloride, especially if your gallbladder has been removed. )  So if your body is producing hydrochloric acid at an extremely low (acidic) pH of 1.5, how does eating beef with a less acidic pH of 5.5 hurt your body? And why would lemon juice with a pH of 2 be better than meat?

Diagram of alkaline Mucous layer in stomach wi...
Diagram of alkaline Mucous layer in stomach with mucosal defense mechanisms (Photo credit: Wikipedia)

So is alkaline blood good for your health?  Well no.  First of all you need to keep your blood essentially neutral with the slightest alkalinity.  Second eating acid or alkaline food has very little effect on your blood pH because you automatically breathe deeper or pee more (but it does affect urinary pH).  And if it were an issue, why do alkaline conditions translate into disease? For instance, low-protein vegans with alkalizing diets tend to have alkaline UTIs.  Mercola believes that alkaline water is only safe for short term detoxification.  A study published in the Journal of Biological Chemistry found that alkalosis (rising cellular pH) causes alkaline-induced cell death as a result of altering mitochondrial function.  Mitochondria are the powerhouses of the cell and their dysfunction causes serious diseases like diabetes and Parkinson’s. Researcher Robert Gilles, who has studied tumor formation and acidity found that tumors make their own acidity even in an alkaline environment.  Scientists developing new anticancer agents that selectively kill tumor cells by interfering with the regulation of intracellular pH, have found that alkaline treatments do not have the desired effect – but strongly acidic treatments do. A  Swedish well water study found that drinking either significantly alkaline or acid water was undesirable, which suggests that drinking water with a pH between 6-8 is best.

Some old studies did show that eating a high meat diet could stimulate the release of calcium in the urine, but that effect stops after a few weeks (and the initial studies were only a week or two long.) Ten years ago a research group at Yale and the University of Connecticut under Dr. Karl Insogna began investigating the effect of dietary protein on bone health, believing that to be true.  Actually it proved that urinary calcium was not from bones, but caused by a more efficient calcium uptake in the gut from dietary protein.

The body has mechanisms to keep the pH (measure of acidity or alkalinity] within a very narrow neutral range of 7.38 and 7.42.  If your blood pH is 6 (slightly acid)  or 8 (slightly alkaline), you can sicken and die.  So your body has a variety of ways to buffer acidity or alkalinity.  The body regulates the acid/alkaline balance primarily through the amount of carbon dioxide ( CO2) exhaled in the lungs and the acidity of urine. If the blood pH drops too low and becomes acid, the body will compensate by increasing breathing, expelling CO2,  so fewer hydrogen ions are free and the pH will rise back to normal. For too much alkalinity the opposite occurs.   Any shifts in acid/alkaline balance in the blood are minor and transient.

 

As Wikipedia says:

The body’s acid–base balance is normally tightly regulated, keeping the arterial blood pH between 7.38 and 7.42.[1] Several buffering agents that reversibly bind hydrogen ions and impede any change in pH exist. Extracellular buffers include bicarbonate and ammonia, whereas proteins and phosphate act as intracellular buffers. The bicarbonate buffering system is especially key, as carbon dioxide (CO2) can be shifted through carbonic acid (H2CO3) to hydrogen ions and bicarbonate (HCO3) as shown below.[2]

rm H_2O+CO_2 leftrightarrow H_2CO_3 leftrightarrow H^++HCO_3^-

Acid–base imbalances that overcome the buffer system can be compensated in the short term by changing the rate of ventilation. This alters the concentration of carbon dioxide in the blood, shifting the above reaction according to Le Chatelier’s principle, which in turn alters the pH. For instance, if the blood pH drops too low (acidemia), the body will compensate by increasing breathing[3] thereby expelling CO2, and shifting the above reaction to the left such that less hydrogen ions are free; thus the pH will rise back to normal. For alkalemia, the opposite occurs.

The kidneys are slower to compensate, but renal physiology has several powerful mechanisms to control pH by the excretion of excess acid or base. In response to acidosis, tubular cells reabsorb more bicarbonate from the tubular fluid, collecting duct cells secrete more hydrogen and generate more bicarbonate, and ammoniagenesis leads to increased formation of the NH3 buffer. In responses to alkalosis, the kidney may excrete more bicarbonate by decreasing hydrogen ion secretion from the tubular epithelial cells, and lowering rates of glutamine metabolism and ammonium excretion.

So my conclusion is that moderation is key, where water should not be significantly far from neutral and food should have a balance of acidity and alkalinity.  Eat real food, organic pasture-raised meat, local fruits and vegetables and don’t sweat the pH.

I don’t endorse this chart, but it shows common beliefs about alkalizing foods.  It isn’t that simple:

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